1. Field of the Invention
The invention relates to an electrically driven actuator.
2. The Prior Art
Such actuators are generally used, but for description of the invention it departs from linear actuators for hospital- and care beds. The beds are typically equipped with a number of actuators for raising and lowering the bed altogether as well as raising and lowering of the back and leg section of the madras. The actuators are cable connected to a central control box containing a power supply for connection to the mains, a rechargeable battery pack, a control connected to one or more hand controls and/or fixed control panels on the bed. The power supply's output voltage is typically 24-48 volt and an upper current of up to about 8 amps.
From a general point of view, among these strength, hygiene, sealing and price, the housing is usually made of plastic material. Overriding is chosen a plastic material which ensures sufficient mechanical strength as all or part of the load on the actuator is transmitted through the housing to the mounting fittings of the actuator.
However, for the electrical equipping of the actuators different demands are made including fire safety demands to prevent fire as a result of defect in the electrical equipment. In certain standards and planned standards for electro medical equipment where effects of more than 15 watts can occur, which is the case more places in an actuator, use of fire-resistant material is allotted. As far as the motor itself is concerned, special measures need not be taken, as the motor housing in it itself is of metal and therefore not immediately flammable. A problem may occur by the closing of openings in the ends of the motor housing. The problem with wires can be solved by using wires which in themselves meet the fire technical demands. Left is then, that the electrical equipment typically also contains print, switches, etc., where effects of more than 15 watt can occur. A possibility would be to make the housing from flame-resistant plastic, but this type of plastic either lacks sufficient strength or is so expensive that it cannot be considered a realistic alternative. A metal housing is also not realistic among other things because of the costs.
The object of the invention is to provide a solution to the noted problem.